Speed changing device



July 14, 1936.

H. E TWOMLEY SPEED CHANGING DEVICE Filed F'ebf25, 1955 6 Sheets-Sheet l July 14, 1936. E TWOMLEY 2,047,840

SPEED CHANGING DEVICE Filed Feb. 25, 1955 6 Sheets-Sheet 2 July 14, 1936. g, E W 2,047,840

SPEED CHANGING DEVICE Filed Feb. 25, 1935 6 Sheets-Sheet 5 July 14, 1936. H. E. TWOMLEY SPEED CHANGING DEVICE Filed Feb. 25, 1935 6 Sheets-Sheet 4 INVENTOR.

ATTORNEYS H. E. TWOMLEY 2,047,840

SPEED CHANGING DEVICE July 14, 1936,

Filed Feb; 25, 1955 6 Sheets-Sheet 5 July 14,1936. E, TWQMLEY 2,047,840

SPEED CHANGING DEVICE Filed Feb. 25, 1935 6 Sheets-Sheet 6 ATTORNEYS Patented July 14, 1936 UNITED STATES PATENT OFFICE- 6 Claims.

My invention relates to speed-changing devices and has particular reference to a power transmission system in which a driven shaft may be coupled to a prime mover to operate at a speed different from the speed of the prime mover.

In power transmission systems wherein a prime mover, such as a motor or other rotary device is employed to drive a driven shaft, the driven shaft may be connected to the prime mover by means of gears, pulleys, belts and the like to operate at a difierent speed from that of the prime mover. However, all such systems which have been employed require the interposition of pulleys of various sizes, or gears of various sizes and ratios, in order to produce the desired speed of the driven member from a given speed of the prime mover, and where the difference in speed between the driven member and the prime mover is relatively great the ratio of gearing or the belting which is required consumes a relatively large space, and further requires considerable complication in their construction.

For example, if amotor is designed to operate at a speed of 1800 R. P. M. and it is desired to drive a shaft therefrom at the rate of 10 R. P. M., the gearing which is required between the motor and thedriven shaft must be relatively large and occupy a great space relative to the size of the motor which is employed to drive the same.

It is an object of my invention to provide a speed-changing system in which substantially any speed ratio between the driven shaft and the prime mover or driving member may be attained by means of power transmitting devices which are relatively small compared with the size of the motor or the prime mover.

Another object of my invention is to provide a speed-changing system of the character set forth in the preceding paragraphs in which a speedch'anging system for producing one speed ratiomay be altered to produce a difierent speed ratio without changing the overall size of the transmission system.

Another object of my invention is to provide a speed-changing system in which relatively great differences in speed between the driving mem-' bar and the driven member may be attained by employing a compact differential type gearing.

Another object'of the invention is to provide a compact difierential gear system which may be employed in the power transmission system wherein the speed ratio between a driving member and a driven member may be altered by relatively small changes in the diameter of gears or pulleys employed in the same.

Another object of the inventionis to provide a variable speed-changing system in which variations of speed ratios between a driving member and a driven member may be attained by a relatively small alteration in'the size of gears or pulleys employed in the system.

Another object of the invention is to provide a transmission system for producing relatively great differences between the speed of a driving member and the speed of a driven member in which two driven gears or pulleys are coupled to the driving member to operate in different directions,- and in which the two driven members or pulleys are coupled to the driven shaft by means of difierential gearing. Other objects and advantages will beapparent from a study of the following specifications, read in connection with the accompanying drawings,

wherein Figure 1 is a vertical elevational view of a motor 0 and driven shaft coupled together by means of a transmission system constructed in accordance with my invention;

Fig. 2 is a plan view of the motor, driven shaft and transmission system shown in Fig. 1;

Fig. 3 is a vertical sectional view taken along line lIIIII of Fig. 2;

Fig. 4 is a detail sectional view, taken along line IV-IV of .Fig. 2;

Fig. 5 is a side elevational view of the motor and pulleys shown in Fig. 1; Figs. 6 and 7 are detail sectional views, .of the motor and pulleys shown in Figs. 1, 2 and 5, i1- lustrating the manner in which the speed of the driven shaft may be variably controlled;

Fig. 8 is a detail, diagrammatic view of a modified form of belt-varying system which may be I employed with the transmission system shown in Fig. 1, through Fig. 7; I

. Fig, 9 is a detail plan view of a multiple pulley and belt drive which may be employed with the form of my invention shown in Figs. 1 through '7; Fig. 10 is an end elevational view of a modified speed-changing system embodying my invention;

Fig. 11 is a plan view of the modified system shown in Fig. 10; I

Fig. 12 is a front elevation, partly in section, of a modified form of difierential unit which may be used in carrying out my invention, and illustrating the adaptation thereof to a planetary gear type of difierential;

' Fig. 13 is a vertical sectional view, taken along line XlIIXIII of Fig. 12; and

Fig. 14 is a detail view of a bearing which may be employed with the form of my invention illustrated in Figs. 12 and 13.

By referring to the drawings, it will be noted that I have illustrated my speed-changing system as employed for the purpose of transmitting power' to a driven shaft directly from a motor, though it will be understood by those skilled in the art that my speed-changing system is equally well adapted to be interposed between any driven shaft and any driving shaft. i

In the embodiment of the invention shown in Figs. 1 through 7, I have illustrated a motor I having a shaft 2 rotated thereby. The shaft 2 has secured thereto two pulleys designated by the reference characters A and B, each of the pulleys being formed of a pair of discs, the pulley A being formed of a disc 3 fixed to the shaft 2 and a movable disc 4 connected as shown in Figs. 6 and 7 to be rotated by the shaft 2 but slidable thereon, as by means of a key 5 engaging a slot 6 in the disc 4, and also engaging a slot I in the shaft 2. In like manner the pulley B is formed of a fixed disc 8 secured in fixed relation upon the shaft 2 and a second disc 9 slidable relative to the shaft 2. In the embodiment of the invention illustrated in Figs. 1 through 7, the disc 9, for the pulley B and the disc 4 for the pulley A, are formed integrally with each other so that sliding movement of the disc members 4-!! will widen the pulley B and narrow the pulley A, or vice-versa, thus adapting the pulleys A and B to a variable speed drive .permittingchange in the effective diameters of the pulleys A and B. by sliding the disc members l9 along the shaft 2, as will be hereinafter more. fully described.

The motor shaft 2 is illustrated as driving a driven shaft l to which the motor and pulleys are connected through a differential driving element designated generally by the reference character C.

The differential driving element consists, essentially, in a pair of rotary members mounted upon the shaft ill in spaced relation to each other and freely rotatable on the shaft with a driven member interposed between the two rotary members having one or more rollers or gears or other power-transmitting devices carried by the driven member to engage both of the rotary members to be driven in the manner of planetary gears, or socalled sun-gears. The rollers referred to may take the form of friction rollers, as indicated in Figs. 1 through 11, or may take the form of beveled gears, or spur gears, as shown in Figs. 12 and 13, so that wherever reference is made herein to rollers it should be understood that this term includes any rolling member which may be employed to interengage the two rotary members of the differential or planetary gear unit.

By referring particularly to Figs. 3 and 4 it will be observed that the driven shaft I0 is rigidly secured to a spider ll, (constituting the driven member of the differential unit), as by means of a key [2, the spider ll extending radially a considerable distance away from the axis of rotation of the shaft l0 and having rotatably mounted being mounted upon the shaft In, these rotary members in the embodiment shown herein constituting pulleys D and E mounted on the shaft Ill on opposite sides of the spider ll, eachof these pulleys D and E being freely rotatable about the shaft l0, and I prefer to interpose ball bearings of the radial and thrust type l6 and I1 between the shaft I 0 and the pulleys D and E, respectively. The inner surfaces of the pulleys D and E are adapted to engage the peripheral surfaces of the rollers l3, which engagement, in the modification shown in Figs. 1 through -11, is a frictional engagement which may be a direct frictional engagement between the material of which the pulleys D and E are constructed with the material 1 of which the rollers l3 are constructed, though I prefer to form the pulleys D and E of relatively strong metal which will engage friction surfaces on the rollers l3, or I may line the inner surfaces of the pulleys D and E with suitable friction material l8, such as leather, rubber, or any of the well-known surfacing materials employed in ordinary friction gear drive systems. Perhaps the simplest construction is that shown in Fig. 3, wherein the friction material I8 is formed as a washer or flat annulus of the friction material 'set into a. recess [9 and held against movement relative to the pulley D as by means of bolts 20. Similarly the friction material l8 for the pulley E may be constructed as a washer set into a recess 2| thereon and held in place by means of bolts 22. Thus the periphery of 'each of the rollers B will be engaged on diametrically opposite sides by the inner surfaces of pulleys D and E, respectively.

From an inspection of Figs. 3 and 4, it will be observed that the pulleys D and E, the spider l I, the rollers l3, and the shaft I 0 constitute a differential gear in which the two pulleys D and E are the driving elements engaging the rollers I3 of the driven element, namely, the spider. Thus if the pulleys D and E are rotated in opposite directions relative to each other and if the speed of rotation of the pulley D exactly equals the speed of rotation of the pulley E, the rollers l3 will be spun around their shafts l4 without causing any.;rotation of the spiderl I. However, if the pulley D is driven at any speed different from the speed at which the pulley E is driven, the roller I 3 will be driven by one of the pulleys D--E at a greater speed than by the opposite pulley and hence the spider will be rotated, drlving the shaft III at a speed determined by the difference in speed between the pulleys D and E. Thus by increasing the difference between the speed of rotation of the pulleys D and E, the speed 5 of rotation of the shaft III will be proportionately increased. For example, if the speed of the pulleys D and E in opposite directions is just equal to-eachoth'er, the resultant drive of the shaft Ill will be zero, while if the speed of the pulleys D and E differ, the resultant driving speed of the shaft III will be equal to one-half of the difference between the speed of D and the speed of E.

Thus, if the pulley D is driven at 500 R. P. M. and

the pulley E is driven at 100 R. P. M., the resultmay be employed to determine the driven speed of the shaft Ill, when r=speed of D and y=speed of the pulley E.

Again, for example, if an extremely low speed is desired for the shaft I0, the difference in speed of operation of the pulleys D and E must be relatively small. Thus if the pulley D is driven at 500 R. P. M., while the pulley E is driven at 499 R. P. M. the resulting speed of the driven shaft ID will be one-half R. P. M.

By coupling the pulleys D and E to the motor I to be driven by the motor I in an opposite di- In the embodiment of my invention illustrated.

in Figs- 1 through 7, I have shown a variable speed drive for the shaft II], in which the pulleys A and B of the motor shaft are arranged by reason of their disc construction to vary their effective diameters.

The pulley A is illustrated as being connected to the pulley E by means of a belt F, illustrated as a double V belt; that is, the cross section of the belt F is formed as a portion of a V-shape extending in both directions from the center of the belt. The belt F is illustrated as being trained over an idler pulley G, then over the motor pulley A, and then over a second idler pulley H, and then over the pulley E. The motor pulley B is coupled to the pulley D by means of a belt K which in this instance extends directly from the pulley D over the pulley B and back over the pulley D. By this coupling arrangement the rotation of the motor shaft 2 ma clockwise direction will drive the pulley D in a clockwise direction and will drive the pulley E in a counter-clockwise direction.

By referring particularly to Figs. 1 and 2 and 5 it will be observed that the idler pulley G is mounted at the upper end of an upstanding bar or bearing support 23, which bar forms one leg of a bellcrank pivoted upon a stub shaft 24 mounted upon a suitable base 25 by means of upstanding bearing members 26 and 21.

It will also be observed by those skilled in the art that the idler pulley H is mounted upon the same stub shaft 24 upon which the bellcrank bearing support 23 is mounted. .It will also be observed that the motor I is secured upon a slide plate 3| supported in slide bearings 32 upon the base 25 so that the motor may be moved toward and away from the shaft III by means 'of an adjusting Screw 33 having a handwheel 34 secured thereto, it being understood that the screw 33 is threaded through an upstanding lug 35 on the base 25 and is engaged with theslide plate 3| in such manner that rotation of the handwheel 34 in one direction-will move the motor I toward the driven shaft I0, while movement of the handwheel 34 in the opposite direction will move the motor away from the driven shaft I0.'

. eter of the pulley A and increasing the effective diameter of the pulley B,- as is shown in Fig. '7,

my invention, in that the pulleys D and E, with while reverse movement of the motor will tighten the belt K and loosen the belt F, reversing the relative effective diameters of the pulleys A and B, as is shown in Fig. 6.

With the construction illustrated in Figs. 1 5 through '7, the adjustment of the motor I relative to the driven shaft I0 to cause the effective diameters of the pulleys A and B to be equal to each other will drive the pulleys D and E at the samespeed, but in the opposite directions, and the driven shaft I will, therefore, not 'be rotated. Movement of the motor I from this position toward the driven shaft I3 will cause the pulley E to be driven at a lesserspeed than the pulley D, and by reason of the differential action of the pulleys D and E on the rollers I3, the driven shaft I will rotate in a clockwise direction at one-half of the difference between the speed of the pulley D and the pulley E. On the other hand, should the motor I be' moved from its original 20 positicn(with the diameters of the pulleys A and B equal)--away from the driven shaft I0, the pulley D will be rotated at a lesser speed than the pulley E, and the driven shaft III will therefore operate in a countenclookwise direction at a speed equal to one-half the difference between the-speeds of the pulleys D and E. It follows, therefore, that by suitably adjusting the position of the motor relative to the driven shaft I0 infinite variation in the speed of the driven shaft 30 I0 may be accomplished.

While as illustrated herein the pulleys A and B are shown as of lesser maximum diameter than the diameter of the pulleys D and E, it will be apparent that by employing larger diameter pulleys in place of the pulleys A'and B, the speed of the driven shaft It! may be greater than the speed of the motor 2, if such stepped-up speed is desired. This brings out an important feature of 40 the rollers I 3 and spider II, may be manufactured in a single, given size. In other'words, the differential unit C may be constructed as a' stock unit and is adapted for the production of any desired speed of operation for its shaft II] by merely substituting pulleys of different diameters for the pulleys A and B. Thus with a single stock differential unit and a series of varying sizes of pulleys A and B for substitution upon the motor shaft 2, an inexpensive infinite variety of speed changes may be supplied with a minimum of parts necessary to accomplish such various speed ratios. The importance of this feature will be apparent by comparing the same with the present type of speed change systems, wherein it is necessary to substitute both the driving pulley and the driven pulley whenever a speed ratio differing from the original speed ratio of the original pulleys is desired. Again, in order to accomplish a relatively great change of speed between the motor and the driven shaft Ill with the present systems ofv transmission, it .is' necessary to use an extremely small diameter pulley on the motor I0 and an extremely large diameter pulley on the driven shaft I0, whereas with my system a relatively small diameter differential unit C on the shaft I0 may be coupled with a pulley set on the motor shaft 2 for substantially the same diameter as the pulley D, thereby insuring that sufficient traction will be provided for the belts K and F even though great speed reduction is desired. Present types of belting systems would require such small diameter pulleys on themotor shaft 2 as to reduce the amount of traction b s-- tween such pulley and its belt to a negligible quantity.

By referring particularly to Figs. 1, 2, 3 and 5, it will be observed that the differential unit C is constructed to be mounted in upstanding bearing members 38 and 38a formed integrally with the base 25, though it will be understood by those skilled in the art that the bearing members 38, 38a may be formed upon a separate unit mounted upon the base 25 if desired. Also the illustration of the invention as shown in Figs. 1 through 7 indicates that the driven shaft II] is parallel to the motor shaft 2, though it will also be understood by those skilled in the art that the driven shaft l may be disposed in any angular relation to the motor shaft 2 if desired and the belts K and F twisted to conform to the annular mountcrank 23 may be moved towardand away from the driven shaft It] to thereby move the idler pulley G to tighten or loosen the belt F. The operation of the bellcrank 23 as indicated keeps the belt F tight at all times and insures sufficient traction between the pulley A and the pulley E, though if desired a compression spring may be interposed between the nut 39 and the leg 28 of the bellcrank 23 to exert a constant force thereon, tending to maintain the belt F in taut relation.

It will also be noted that the friction engage- ,ment between the pulleys D and E and the rollers l3 may be maintained at any desired value by mounting one of the pulleys D or E for sliding movement relative to the shaft. l0 and relative to the other pulley D or E, as is shown particularly in Fig. 3, wherein the pulley D is mounted for sliding movement toward the pulley E and the frictional engagement between the pulleys D and E and the rollers I3 is maintained by means of a compression spring 39 interposed between the bearing member 38 and the ball bearings IS on which the pulley D is mounted.

In the form of the invention shown in Figs. 1 to 7, the motor may be initially adjusted to produce a predetermined tautness upon the belt K and then by adjusting the nut and bolt 29, 30 the belt F may be adjusted to an equal tautness. When this adjustment is made, shifting of the motor I, relative to the driven shaft I, will not' change the relative tautness of belts K and F but will merely change the relative effective diameters of the pulleys A and B.-

As is shown, however, in Fig. 8, the effective diameters of the pulleys A and B may be varied by simultaneously tightening belt K and loosening belt F, or simultaneously loosening belt K and tightening belt F by a belt-shifting mechanism instead of shifting the relative position of the motor and the driven shaft in. In the embodiment of the invention shown in Fig. 8, it is assumed that the driven shaft l0 and the motor shaft 2 are fixed relative to each other and that the beltsK and F extend between pulleys D and may be readily formed by merely providing three belt grooves in a wide-faced single pulley substi- L and M are mounted upon a yoke 40 pivoted upon a shaft 4| secured to the base 25a upon which the motor I and the driven shaft l0 may be mounted. The yoke 4| is provided with a downwardly extending arm 42 engaged with an adjust- 5 ing screw 43 threaded into an upstanding lug 44 rising from .the base 25a. The mounting of the. pulleys L and M is such that the pulley L engages above the belt F, while the pulley M engages below the belt K. Thus by moving the screw 43 toward the right, as viewed in Fig. 8, the belt K will be tightened, while the belt F is simultaneously loosened, thus reducing the effective diameter of the pulley A and increasing the effective diameter of the pulley B. Reverse movement of the screw 43 will, in like manner, tighten belt F and loosen belt K and reverse the relative diameters of the pulleys A and B and thus provide for varying the relative speed of operation of the pulleys D and E on the differential unit C.

While in the embodiment of the invention shown in Figs. 1 through 7 it is assumed that but a single pulley D is used upon the differential unit C and a single pulley E is used upon the differential unit C, the transmission of relatively great 5 amounts of power from a driving shaft to a driven shaft may be required and greater traction than will be provided by the single pulley and the single belt arrangement shown therein. My system, however, is equally well adapted to a multiple belt 30 drive, as is illustrated particularly in Fig. 9, wherein the motor shaft 2 is illustrated as being provided with a set of belts corresponding to the pulleys A and B shown in Figs. 1 to 7. In this instance, however, three pulleys, Al, A2 and A3 35 are employed as a substitute for the single pulley A, while similarly pulleys Bl, B2 and B3 are substituted for the single pulley B. The pulleys. Al, A2 and A3 may be formed of a single fixed disc 45 and a plurality of slidable discs 46, 47 and 48. Similarly, pulleys Bl, B2 and B3 may be constructed of a single fixed disc 49 and slidable discs 58, 5| and 52, again the disc 52 constituting one end of the pulley system Bl B2 and B3 which may be formed integrally with the disc 48 constituting the end disc of the pulley set Al A2 and A3, so that by tightening the belts Fl, F2, and F3, passing over the pulley set Al, A2 and A3, and loosening belts Kl, K2, and K3, passing over the pulley set Bl, B2, and B3, will slide all of the slidable discs 46,41, 48, 52, 5| and to the right as viewed in Fig. 9, while tightening belts Kl K2, and K3, and loosening belts Fl, F2, and F3, will cause the slidable discs to move toward the left, thus varying the effective diameters of the pulley set Bl, B2 and B3 relative to the pulley set Al, A2 and A3. The single pulley D of the differential unit C is illustrated in Fig. 9 as having been substituted for by three pulleys DI, D2 and D3 which tuted for the narrow pulley D. Similarly, the three pulleys El, E2 and E3 are substituted for the single pulley E. Again such construction may be in the form of three belt grooves formed in a single wide-faced pulley substituted for pulley E. Internal mechanism, including rollers l3, spider II and its connection to shaft l0 may be identical with that described with reference to Figs. 1 through '7. Also it will be noted that the tig'hten ing and loosening of belts Fl, F2 and F3, and Kl K2 and K3, may be accomplished either by shifting the motor relative to the shaft ,ll! or by employing a belt tightening and loosening system as shown in Fig. 8.

.drive for the driven shaft I but at a differentspeed from the speedof the motoror other driving shaft.

By referring particularly to Figs. 10 and 11,- it will be noted that I have embodied in my transmission system employing the differential unit C as a speed-reducing transmission system applicable to a constant speed, a motor Ia for driving a shaft I0a at a constant speed. In this embodiment of my invention the motor Ia has its shaftla provided with a pair of pulleys Aa, Ba, over which operate respectively belts Ka and Fa. In this embodiment of the invention the beltsKa and Fa are shown as relatively wide, fiat belts-which engage relatively wide peripheral surfaces of the pulleys Au and Ba. Similarly, the differential unit C'isidentical with the unit shown in Figs. 1 through 7 except that wide-faced pulleys Ea and Da have been substituted for the V-grooved pulleys D and E. The pulleys Aa and Ba will be formed with their diameters differing from each other by such amounts as will produce the desired difference in speed of the pulleys Ea and Da to achieve the necessary speed reduction for the shaft Illa.- If desired the pulleys Ba and Ac may be formed as a single integral unit secured to the shaft 2a .as by means of a set screw 53. Thus it will be observed that with a single stock differential unit C innumerable variations in the driven speed of -the shaft l0a may be obtained, by the mere substitution of pulleys for the pulleys Aa and Ba in which the relative diameters of these pulleys differ by different amounts. This permits a.

manufacturer to stock a quantity of the same size differential units C together with a quantity of different diameter pulleys Aa and Ba adaptable for substantially any speed ratio between the motor Ia and the driven shaft Ifla. Again it will be noted that the diameter of the differential unit C may be maintained above relatively small limits and that substitution of varying diameter pulleys Aa and Ba may be made without requiring additional gearing or without requiring enlargement of the differential unit C. Thus a relatively small compass substantially infinite speed ratios may be obtained as distinguished from the systems now in use which require enlargement of the total size of a speed-changing unit as the speed ratio increased.

With the form of the invention shown in Figs. 10 and 11 the belt Ka, like the belt K, is drawn over a pair of idler pulleys Ga and Ha in order to permit rotation of the motor shaft 20. in the same direction to drive the differential unit pulleys Errand Da in oppositedirections. The support or mounting for the pulley Ga, comprising a lever 54 pivoted upon a suitable stub shaft 55 mounted in an upstanding bracket 56 extending from the base 51, upon which the motor la is mounted and also upon which the bearing members 58 and 59 for the driven shaft We are mounted. One end of the lever 54 maybe connected by a suitable spring 60 to an adjusting screw BI having a nut 62 thereon which maybe tightened or loosened to vary the tension on the lever 54 to thereby hold the belt Ka tight at all times.

In order to insure that the belt Da may also be maintained in taut relation upon its pulleys, the motor Ia may be mounted upon a secondary base plate 53 pivoted to the base 51, as indicated at 64, with a spring 65 secured to an eye-bolt 66 normally urging the motor base plate 63 toward the base 5'I.

. Referring particularly to Figs. 12, 13 and 14 I have illustrated a still further modified form of the invention in which the differential unit is constructed after the pattern of the planetary or sun-gear type of transmission. The driven shaft I0d may be supported in any suitable bearing members, not shown, similar to the bearing supports 58 and 59, as illustrated in the form of the invention shown inFig. 11 and has freely rotatable thereon a flat disc pulley member I20, the outer periphery of which is grooved, as indicated at I2I, to receive a double V-belt I22. Secured to the rear face of the disc pulley I 20 is a cup-like member I 23, also freely rotatable upon the shaft I0d, as by interposing a roller bearing I24 between the cup I23 and the shaft I0d. The cup-like member I23 is secured to the pulley disc I20 by means of a plurality of screws Him that by driving the pulley I20 the cup member I23 will likewise be driven at the same speed.

Formed internally within the periphery of the cup-member I23 is an internal gear I26 adapted to mesh with a pinion I 21 rotatably mounted upon an outstanding boss I28 formed upon a spider [29. A second pulley I30 is rotatably mounted upon the shaft I0d as by means of a ball bearing I3I, the pulley I30 being adapted to receive a V-belt I32. The pulley I30 is keyed as indicated at I33 to a sleeve I34, the lefthand end of which, as viewed in Fig. 13, is enlarged to form a spur gear I35 also'meshin'g with the pinion I21. The spider I29 is keyed, as indicated at I36, to the driven shaft I0d so that by driving the pulley I30 in one direction and driving the pulley I20 in the opposite direction, the pinion I21 will act'upon the gears I26 and I35 in the same manner as the rollers I3 were acted upon by the pulleys D and E inthe form though it will be understood by those skilled in the art that the diameter of the pulley I30 may be increased or decreased relative to the diameter of the .pulley I20 to achieve the desired ratios between these two pulleys.

It will be particularly observed from an inspection of Figs. 12 and 13 that the unit illustrated therein is adapted for simple lubrication, since the cup-like member I23 assembled with the pulley disc I20 forms a hollow chamber I31 which may befilled with suitable oil, grease or other lubricant, and by employing ball bearings of the type shown in Fig. 14 as the ball bearings I24, I38 and I39, this chamber may be made substantially leakproof. 7

By referring particularly to Fig. 14 it will be observed that the top ball bearing I39 illustrated therein includes the ball races I40 and MI engaging the balls I42. Interposed between the *ball races I40 and MI on both' sides of the balls I42,

are washer assemblies including a packing mem- 75 4 ber I43 made of felt or other material which .will form a seal between the two ball races.

In the form of the device shown in Figs. 12 and 13,. I have shown the spider as being provided with two pinions I2! located at diametrically opposite sides of the driven shaft Hid, though it will be understood by those skilled in the art that if desired a single pinion l 21 may be employed with this form of the device without serious unbalancing of the unit. a

While I have shown and described the preferred embodiment of my invention, it is to be understood that I do not wish to be limited to any of the details of construction shown herein, except as defined in the appended claims.

I claim:

1. In a speed changing system; a differential unit, including a pair of rotary membersflan intermediate member interposed between said rotary members and one or more rollers carried by said intermediate member interengaging both of said rotary members, a drive shaft, a pair of variable diameter pulleys on said drive shaft, a belt coupling one of said differential unit members to one of said pulleys for driven movement in the same direction as said pulley, antother belt coupling the other of said pulleys to another of said differential members to drive the same in the opposite direction, a driven shaft connected to the third differ ential element, and means for simultaneously varying the diameters of said pulleys inversely relative to each other to vary the speed of said driven shaft without variation of speed of said drive shaft.

2. In a speed changing system, a differential unit, including a pair of rotary members, an intermediate member interposed between said rotary members and one or more rollers carried by said intermediate member interengaging both of said rotary members, a drive shaft, a pair of cone disc pulleys on said drive shaft, a belt coupling one of said differential unit members to one of said pulleys for driven movement in the same direction as said pulley, another belt coupling another of said pulleys to another of said differential members to drive the same in the opposite direction,

- a driven shaft connected to the third differential element, and means for simultaneously varying the effective diameters of said cone pulleys inversely relative to each other.

3. In a speed changing system, a differential unit, including a pair of rotary members, an intermediate member interposed between said rotary members and one or more rollers carried by said intermediate member interengaging both of said rotary members, a drive shaft, a pair of cone disc pulleys on said drive shaft having a cone disc common to both pulleys, a belt coupling one of said differential unit members to one of said pulleys for driven movement in the same direction as said pulley, another belt coupling the other of said pulleys to another of said differential members to drive the same in the opposite direction, a driven shaft connected to the third,di1ferential element, and means for shifting said common cone disc longitudinally of said drive shaft to simultaneously vary the effective diameters of said pulleys inversely relative to each other.

4. In a speed changing system, a difierential ed in spaced relation to said drive shaft upon ,the

opposite side thereof, a belt directly coupling one 10 of said differential members to one of said pulleys for driven movement in the same direction as said pulley, another belt extending from the other of said pulleys over saididlers, and another of said differential members to drive the same in the opposite direction, a driven shaft connected to the third of said differential members to be driven thereby, and means for simultaneously varying the diameters of said pulleys inversely .relative to each other to vary the speed of said driven shaft; 20 5. In a speed changing system, a differential unit, including a pair of rotary members, an intermediate member interposed between said rotary members and one or more rollers carried by said intermediate member interengaging both of said 25 rotary members, a drive shaft, means mounting said diiferential unit spaced to one side of said drive shaft, a pair of cone disc pulleys on said drive shaft having a cone disc common to both of Said pulleys shiftable along the length of said shaft, a pairof idlers mounted in spaced relation to said drive shaft upon the opposite side thereof, a belt directly coupling one of said differential members to one of said pulleys for driven movement in the same direction as said pulley, another belt extending from the other of said pulleys over said idlers and another of said differential members to drive the same in the opposite direction, a driven shaft connected to the third of said differential members to be driven thereby, and 40 means for simultaneously tightening one of said belts and loosening the other thereof for varying the effective diameters of said pulleys and inversely relative to each other to vary the speed of said driven shaft.

6. In a speed changing system, a differential unit, including a pair of rotary members, an intermediate member interposed between said rotary members and one or more rollers carried by said intermediate member interengaging both 50 of said rotary members, a drive shaft, means mounting said differential unit spaced to one side of said drive shaft, a pair of variable diameter pulleys on said drive shaft, a pair of idlers mounted in spaced relation to said drive shaft upon the 55 opposite side thereof, a belt directly coupling one of said differential members to one of said pulleys for driven movement in the same direction as said pulley, another belt extending from the other of said pulleys over said idlers, and another of said 30 differential members to drive the same in the opposite direction, a driven shaft connected to the third of said differential members to be driven thereby, and means for shifting said driven shaft toward and away from said differential unit to 65 simultaneously vary the effective diameters of said cone inversely relative to each other to vary the speed of said driven shaft.

. HERBERT E. TWOMLEY. 

